In this project, an old IBM point-of-sale (POS) display is reverse engineered to display arbitrary text.
The goal of this project is not entirely clear.

The display in question contains two rows of 20 characters each.
The characters on the display are of the VFD type, in blue/cyan.

The display has the following markings on its PCB:
Futabacorp KU-02194V-O N

Interface

The electrical interface to the display consists of 4 wires, possibly:

ground

data A (inverting), D-

data B (non-inverting), D+

power (12V) - red

This is most likely an RS485 interface, because there is a 75176 (differential bus transceiver) inside the display.

A very simple RS232-to-RS485 conversion can be done by simply biasing the inverting data pin (data A) to half the supply voltage, and connecting the RS232 data line directly to the non-inverting data pin (data B).